Pollution control devices are employed on motor vehicles to control atmospheric pollution. Such devices include catalytic converters and diesel particulate filters or traps. These devices include a pollution control element. For example, catalytic converters typically contain a ceramic or metal monolithic structure that supports the catalyst. The catalyst oxidizes carbon monoxide and hydrocarbons, and reduces the oxides of nitrogen in engine exhaust gases to control atmospheric pollution. In addition, diesel particulate filters or traps typically contain a wall flow filter in the form of a honeycombed monolithic structure, usually made from porous crystalline ceramic materials. Each of these devices has a metal housing (typically stainless steel) which holds or mounts the pollution control element.
Such pollution control elements are typically fragile and susceptible to vibration or shock damage and breakage. The damaging forces may come from rough handling or dropping during engine assembly, from engine vibration or from travel over rough roads. Such pollution control elements are also typically subject to damage due to high thermal shock, such as from contact with road spray. To protect the pollution control element, especially the ceramic monolithic type, and to prevent exhaust gases from passing between the pollution control element and the surrounding housing (thereby bypassing the catalyst or filter), mounting mats are disposed between the pollution control element and the housing.
Some mounting mats and insulating elements (e.g., end cone insulation) include mostly inorganic fibers, with inorganic or organic binders, fillers and the like. Such mounting mats are commonly die cut, using metal blades, out of larger sheets of the inorganic fiber material.
The present invention provides an improvement to such prior mounting mats and insulating elements.